Water rarely kills a phone instantly. Damage happens when power flows through wet circuits, or later when minerals left behind corrode contacts. That is why a phone can work for a day and then fail.
The immediate priorities are simple: power off, do not charge, remove any case and SIM tray, and dry the outside. Charging a wet port is the single most common way a survivable soaking becomes a repair.
Rice does almost nothing and adds dust and starch to the ports. Air movement at room temperature is far more effective, and heat sources warp seals and batteries.
Water-resistance ratings help but age. Seals degrade after drops and years of thermal cycling, so a phone rated for immersion when new may not be after two years.